"They see this as a huge advantage, being able to come to North America to work and ply their trade and make a lot of money."

Once they arrive here, Drennan said, the women are told that they have to work off a $30,000 debt before they are allowed to go free.

'We think... from five to 10 new women are brought here every month'
-- Anne Drennan

But their keepers charge them $10 a day to eat at fast-food restaurants and $10 a day for condoms.

The women are given heroin to smoke three times a day and quickly become addicted.

"At the end of the week, even though the girls have been turning tricks and apparently earning money to pay off their $30,000 debt, they end up owing their keepers," said Drennan. "So there's no profit and no opportunity to pay off their debts."

The women, aged between 20 and 32, are allowed to go out unaccompanied for meals. But they keep coming back for the drugs.

"It's the heroin that turns them into slaves," said Drennan. "They don't know the ways of the world here or have other contacts, so they have no other way of getting their heroin."

The ring, which is believed to also involve the notorious Big Circle gang in Vancouver, smuggles women from Vancouver south to Los Angeles or est to the Toronto area, where the "debts" still hold.

"We think... from five to 10 new women are brought here every month," said Drennan. "We think this is probably the low end in the numbers."

Drennan said the women in the safe houses have not been charged and police hope they will stay to testify in court.

"Obviously we would like them to be here long enough to testify, but if in fact they are deported pre-testimony, so be it."

The arrests are linked to a crackdown in Ontario last fall, in which several bawdy houses were raided.

Charged with keeping a common bawdy house are Ping Kwong Mak, 28, and Sui Mui Ko, 28, both of Vancouver.

Also charged with the same offence are Hong Deng, 35, and Cheng Zhi Zhao, 27 both of Richmond.